Heteroepitaxial Ge1-xSix layers on Si(100) with high Ge contents are of interest due to many applications in key technologies such as solar cells, MEMS, quantum cascade lasers and Si-based photonics (see, Mooney, P. M.; Chu, J. O. Annu. Rev. Mater. Sci. 2000, 30, 335; and Tromp, R. M.; Ross, F. M. Annu. Rev. Mater. Sci. 2000, 30, 431), including high speed modulators and photodetectors (see, Kuo et al., Nature 2005, 437, 1334). However, these materials are much less developed in spite of this high impact potential in IR optical devices. In addition, they serve as virtual substrates for growth of high mobility, strained Si and Ge device channels, and are also considered as a potential pathway to monolithic integration of III-V based devices with Si technologies (Lee et al., J. Vac. Sci. Technol. 2004, B 22 (1), 158; and Kasper, E.; Heim, S. Appl Surf. Sci. 2004, 224, 3). The best current route to these materials is complicated and fraught with difficulties, requiring both high temperature growth of thick (>10 μm) compositionally graded films and a chemical-mechanical planarization step to relieve the misfit strain between the Ge1-xSix epilayer and Si substrate and produce a flat surface, respectively (see, Currie et al., Appl. Phys. Lett. 1998, 72 (14), 1718).
Chemical vapor deposition (CVD) methods that allow growth of Ge-rich (Ge≧50 atom %) device-quality alloys on Si that cannot be obtained by conventional routes have been recently developed (see, Ritter et al., J. Am. Chem. Soc. 2005, 127(27), 9855-9864; Hu et al., J. Appl. Phys. Lett. 2005, 87(18), 181903/1-3; and Chizmeshya, et al., J. Am. Chem. Soc. 2006, 128(21), 6919-6930). Ge-rich films can enable higher speeds in microprocessors, lower power consumption in cell phones, silicon-based photonics, and more efficient solar cells (see, Mooney and Chu, supra; and Tromp and Ross, supra). The technology utilizes previously unknown designer Si—Ge hydride precursors to precisely control the chemical composition, morphology, and microstructure of the corresponding films, circumventing the need for thick graded layers and lift off techniques (see, Currie et al., supra).
To prepare such semiconductor structures, SidGe1-d alloys can be deposited selectively in, for example, the source and drain regions of a transistor architecture. Conventional selective growth of SidGe1-d alloys is achieved using high temperature reactions of chlorosilanes, germane and elemental Cl2 which typically do not yield films with suitable morphology and microstructure in the high Ge concentration range. For example, selective growth of SidGe1-d alloys has been achieved using high temperature reactions of chlorosilanes, germane and elemental Cl2. However, the complexity of the associated multicomponent reactions and the presence of corrosive Cl2 call for alternative approaches to selective growth. This need is particularly acute in the high Ge-concentration range, for which the chlorosilane route does not yield selectively deposited films with suitable morphology, microstructure or composition. Furthermore, for high Ge content the conventional processes lead to high dislocation densities, non-uniformities in strain, lack of compositional control, and reduced film thickness, all of which ultimately can degrade the quality and performance of the stressor material thereby limiting the practical usefulness of this approach.
Therefore, there exists a need in the art for methods for the deposition of SidGe1-d materials, methods for the selective deposition of SidGe1-d materials, and in particular, high Ge content SidGe1-d materials on substrates which avoid the issues described above.